TL;DR:
The root cause of the Technical-mode glitch is still unknown (actually I think maybe I was mixing up different modes and now I think I figured it out by going through the mode settings)
so maybe ignore me, but thanks for hanging out, cause Rhino forum is awesome
… Switching to any other display mode (I chose ‘rendered’) and back to Technical is the only reliable bypass. After doing that, the viewport and exports match, but Technical stops generating one of the lines because of its own shading/edge-generation effects — the issue is inside Technical’s line logic, not in Print or ViewCaptureToFile.
Ok so after going through all the settings of the default technical mode and changing all of them I became more familiar with them again and got the results corrected more now with 99.9% satisfaction